Pollen grains (green) on the foot of a bee, coloured scanning electron micrograph (SEM). Pollen grains are the male sex cells of a flowering plant. They adhere to the bodies of insects when the insects alight on flowers to feed on the nectar they produce. As the insects travel from flower to flower, some of the pollen grains are transferred to the female parts of another flower (pollination). Bees are a major pollinator of flowering plants. Magnification unknown.